perf machine: Introduce synthesize_threads method out of open coded equivalent

Further simplifications to be done on following patch, as most tools
don't use the callback, using instead just the canned
machine__process_event one.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-r1m0vuuj3cat4bampno9yc8d@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/machine.c

@@ -1394,3 +1394,15 @@ int machine__for_each_thread(struct machine *machine,
 	}
 	return rc;
 }
+
+int machine__synthesize_threads(struct machine *machine, struct perf_tool *tool,
+				struct perf_target *target, struct thread_map *threads,
+				perf_event__handler_t process, bool data_mmap)
+{
+	if (perf_target__has_task(target))
+		return perf_event__synthesize_thread_map(tool, threads, process, machine, data_mmap);
+	else if (perf_target__has_cpu(target))
+		return perf_event__synthesize_threads(tool, process, machine, data_mmap);
+	/* command specified */
+	return 0;
+}